towards 3D data model

[Philippe Prugniel]

Doug Tody wrote:

>For modeling 3D data in DAL, more is required as we need to model the
>actual dataset.  Currently we have 2D sky images (SIA) and various kinds of
>tabular spectrophotometric data (SSA).  My feeling is that what is required
>for spectral datacubes is a generalization of the 2D image model to 3D.
>This would build upon the spectrophotometric metadata developed for SSA to
>describe the observable, plus FITS WCS to describe the coordinate system.
>  
>

All 3D data cannot be easily formatted as regularly sampled data. There 
are several particular
cases and the most general model would be to represent them as 
collections of SED
(except for representing multicolor images with a slightly different WCS 
in each image).

Of course it would be good to be able to use a spatial WCS when it is 
possible, and a
spectral WCS when possible also.

>We need to understand the science
>drivers better to analyze this, i.e., what sorts of analysis do we want
>to target with this capability.
>  
>
I think it is the right way to proceed.
First define science cases and the type of data we want to handle. And try
to keep as simple as possible.

>>dear Giovanni, Phillipe and Igor,
>>   I am happy that Euro 3D people will join the IVOA data model effort
>>This connection was missing since a long time. I am not personnaly sure
>>    
>>
Just a precision: Neither myself or Igor belong to Euro 3D (we are 3D 
users), so I am not sure
yet how far you should consider that the E3D people join the IVOA DM 
effort; I hope they
will...

Sincerely. Philippe.